1. Field of the Invention
This invention relates to a method for producing printed surfaces which fluoresce under ultraviolet (UV) light.
2. Description of Related Art
It is known to use fluorescent dyestuffs in combination with normal dyestuffs for various effects.
Fluorescent dyestuffs are mixed with normal dyestuffs to make the color brighter in daylight. The dyestuffs which are non-visible or fluoresce under ultraviolet light (UV light) are also particularly used in the theatre for special effects, their dramatically fluorescent properties under UV illumination being exploited.
It is known that for use in signs and in advertising, adhesive, fluorescent foils are cut into letters and/or figures, emblems, logos and the like, which for example are stuck to a window pane or to a corresponding pane or panel made of glass, Plexiglas or a similar translucent material that forms a carrier for signs or advertising.
In order to impart the desired, glowing, neon-like effect to the sign or advertisement, it must be illuminated by a so-called non-visible or black light.
An adhesive, fluorescent foil with a translucent layer, which is impermeable or substantially impermeable for UV radiation, is disclosed in PCT International Publication WO-A-93/01581.
A disadvantage in the use of such adhesive, fluorescent foils in the form of cut-to-size letters, figures, emblems, logos and the like, in signs or in advertising is that merely letter features, logos and uniform color areas can be highlighted, and photographic reproductions and pictures in general cannot be depicted in color gradations and transitions. Furthermore, it is disadvantageous that numerous foil characters or patterns must be fabricated and cut in complex individual steps and the individual, monochrome foil patterns must be positioned and glued by hand within the scope of the actual formation of the sign or advertising surface.
A method is known from U.S. Pat. No. 4,652,464, for printing art or advertising graphics using visible and/or non-visible, fluorescent dyestuffs and non-fluorescent dyestuffs in multiple print series of colors, each print series being implemented with one predetermined print pattern. Art and advertising graphics are produced in the printing process with the property of depicting an object with a smooth transition under distinctly different lighting conditions when the object is observed under illuminations which vary between daylight or incandescent light up to UV light.
In this method visible and/or non-visible, fluorescent dyestuffs are used during the printing process, which are applied to previously selected areas of the picture in a predetermined pattern, in order to obtain the desired colors under normal light or daylight and in order to amalgamate these fluorescent dyestuffs with the non-fluorescent dyestuffs under UV light, so that the fluorescent dyestuffs are blended or concealed under normal light.
The relative ratio and the colors and different color tones of the non-fluorescent dyestuffs and of the visible and non-visible, fluorescent dyestuffs are selected in advance, in order to achieve a gradual, fine transition on the picture when it is observed under light conditions which alternate between daylight and UV light, or in order to blend or shade the effect, or in order to reduce the intensity of the fluorescent dyestuffs in specific areas so as to achieve a more natural and gentler effect under UV light.
The disadvantage of the method according to U.S. Pat. No. 4,652,464 is that the printing process must be modified in a complex manner in order to include the application in addition of fluorescent dyestuffs. Also, a printing process is required which is structured in many printing steps with the application of a multiplicity of specific fluorescent dyestuffs and, furthermore, predetermined areas with gradations both of the normal colors and also of the non-visible, fluorescent dyestuffs must be printed, in order to examine the desired effect of not impairing the fluorescent dyestuffs, which are applied to the picture, by the normal daylight dyestuff patterns.
A method for producing surfaces which are luminous at night is known from German Patent Reference DE-A1-196 20 090, in which a wire printer method with luminous colors red, green, blue is used so that the printed surface is luminous at night. In a second print run with translucent colors the motif depicted on the printed surface can also be made visible in daytime. The second print run serves at the same time as UV and reaction protection of the luminous colors.
One object of this invention is to provide a method that avoids the required multiplicity of printing steps and in particular the complex adjustment of the fluorescent colors in the printing process.
This object is achieved by features of this invention as described in the claims and this specification.
Particular requirements or additional steps are no longer required. Non-visible, fluorescent dyestuffs were not used in the mentioned form in the four-color and multi-color printing method. The advantages of this invention reside particularly in the fact that, instead of a multiplicity of printing steps using non-visible, fluorescent print colors and paints, the normal practice printing steps are implemented. In this connection, as also with four-color and multi-color printing with the conventional primary colors, in the lithographic composition an authentic pictorial reproduction is effected by targeted alteration of the color parameters of each individual print color and in the printing itself a fine adaptation of the perceived color is effected by an alteration of the applied color quantity. This alteration method which is known to any printer can immediately be implemented without special training or other know-how in a non-problematic manner.